Resistance to Multiple Fluoroquinolones in a Strain of Streptococcus pyogenes: Detection of Point Mu A strain of S. pyogenes was isolated from the blood of an 18-year-old patient with Jobs syndrome who had recently received various antibiotic treatments including levofloxacin. Susceptibility testing demonstrated the isolate to be resistant to the fluoroquino-lone antibiotics. DNA gyrase A and topoisomerase IV are the dual targets for quinolones. Resistance to this class of antibiotics has not been studied in S. pyogenes. Quinolone resistance-determining regions (QRDR) of both the parC subunit of topoisomerase and DNA gyrase A are conserved in a number of bacteria belonging to different genera. We designed PCR primers flanking the QRDR of these two genes from S. pyogenes based on the amino acid sequence homologies among S. pneumoniae, E. coli, and S. aureus. The amino acid sequences deduced from the amplified gene products from S. pyogenes demonstrated significantly high homology to the same regions of these two genes in S. pneumoniae. Compared to the quinolone sensitive ATCC strain, the quinolone-resistant isolate of S. pyogenes presented point mutations in DNA gyrase A and in the parC subunit of topoisomerase IV. We will perform susceptibility testing and will sequence the QRDR of several recent isolates of S. pyogenes to support our claim that the resistant isolate we have sequenced is unique.